Fire alarm system



Dec. 20, 1949 w. s. HOLMES FIRE. ALARM SYSTEM Filed April 3, 1.948

Patented Dec. 20, 1949 UNITED STATES- PATENTv OFFICE FIRE ALARM SYSTEMWillis Gerald Holmes, Hanover, Mass., assigner to The Protectowire C0.of Maine, Augusta, Maine, a corporation of Maine AApplication.April 3,1948, Serial No. 18,743

9 Claims. l

' An analytical survey of any representative selection of seriousconfiagrations clearly shows that a delay in discovery makes thediiierence between a small easily controlled re and a major disasterresulting from its neglect. This need for prompt discovery of anincipient lire has long been recognized and many systems and deviceshave been developed to control and indicate the `presence of such ai'lre. Functionally, these devices are divided into two general groups.

One group includes systems with automa-tic detectors (responsive, forexample, to the flow of water in a sprinkler system or to a thermostat)to operate electrical contacts thereby tra-nsmitting an alarm signal bymeans of an electrcal circuit. The preferred type of Such systemcomprises fundamentally a plurality of detec-tors with normally openelectrical contacts for interconnecting two parallel conductors whichare connected in series with a terminal resistor and` a power source.The closing of any one of these contacts in response to a change inambient temperature shunts the terminal resistor thereby decreasing thetotal resistance of the circuit. The resulting increase in the flow ofcurrent is used to operate a switching element of an associated alarmcircuit, to open a sprinkler system or to initiate Afunctioning of otherfire preventive means.

The other group includes the systems with manually operated alarmstations for transmitting an alarm signal to a central station or to thenre department. Highly developed systems, of this type transmit codedsignals in response to rotation of a spring actuated code wheel whichinterrupts a series connectedelectrical initiating circuit continuouslyenergized from a `power source so vas to be self-supervising.

Because of the danger of panic `in'public buildings such as hotels,theaters and schools, 'a general alarm should not be sounded unless itis absolutely necessary for the safety of the occupants. The commonmeans for accomplishing this end is to have the signal transmitted uponringing any one of the Aabove-described alarm stations, give apreliminary alarm at la central station in the usual manner. If after aninvestigation a general alarm is found necessary. it is sounded from thenearest alarm station bv means of a special key carried bytheinvestigator.

The ldetecting and alarm svsten'frs are not `generally combined in onesystem `despite the "ob-` vious advantages in simplicity, economy andmaintenance such an arrangement `would have.

If alarm detecting devices of the conventional type are used in the sameelectrical initiating circuit with series type manual alarm stations,the operation of any one ofthe detecting devices shunts the two parallelconductors so that the alarm stations positioned in the loop beyond theshunt with respect to the power source are rendered inoperative. Theinterruption of the systernby the operation of one of the detectingdevices also prevents 'the use of the alarm stations to sound a generalalarm. If an automatic detector with a normally closed contact isconnected in series with the initiating circuit, the interrupting.action has the same electrical effect upon supervisory elements of thecircuit as a ground or power failure so that the system does notdistinguish a nre signal from a trouble signal.

Objects o'f` this invention are to provide an electrical system whichincorporates both manually operated alarm stations and automaticallyoperated detecting devices in the same initiating circuit, whichtransmits coded signals, which rst transmits a preliminary alarm eithermanually or automatically land which subsequently permits the manuallysounding of a general alarm, and to provide such a system which isdependable and electrically self-supervising,

which is simple and. economical to install :and

maintain, and which advances vthe art of fire alarm and detectiongenerally.

In a broad aspect the invention contemplates a signalling systemcomprising two conductors and a .resistor connected in series with apower source to complete a continuously energized double loop initiatingcircuit. Each of a plurality of alarm stations is connected toY transmita signal by simultaneously opening both conductors thereby to interruptthe initiating circuit.. A.

signal is also transmitted by changing theresistance of the initiatingcircuit by interconnecting the conductors thereof by means oi any one of`a plurality `of detecting stations. A switching element, responding toa first signal from one of the stations, connects a preliminary alarmcircuit .and also a time `delay device in a general alarm circuit withthe power source. After the operation of the time delay device theswitching `element is 'responsiive to subsequent signals to energizeboth the preliminary and* general alarm circuits.

In a different aspect the alarm circuitor circuits are energized 'from`the same or different power sources: by the' use 'of ftw'o switchingelements. `One `of these switching elements connects the alarm circuiteitherin response to a 3 signal resulting from the interruption of theinitiating circuit by one of the alarm stations or in response to theoperation of a second switching element by a signal from one of thedetecting stations.

In a more specic aspect the switching element or elements are relayseach having one or more contacts operated by a respective solenoid inresponse to signals from one of the stations. The interruption of theinitiating circuit by one of a plurality of manually-operated alarmstations deenergizes the solenoid of a signal relay connected in seriestherewith to close three contacts in the preliminary alarm circuit,general alarm circuit and latching relay circuit respectively. Thedecrease in resistance of the initiating circuit resulting from theoperation of one of a plurality of automatically operated code stationsresults in an increase in the current flowing therein so that thesolenoid of a second relay is energized to release a detent restrainingan automatically operated code wheel. A normally closed contact inseries with the initiating circuit is opened in response to the rotationof the code wheel thereby deenergizing the signal relay and energizingthe alarm circuit.

An additional feature is the closing of a normally open contact by theenergization of a coil of a latching relay circuit by the signal relay,to connect a heater element of the time delay device to the powersource. A latching relay is provided toA maintain the contact in thisposition until manually released. After a predetermined time intervalthe rise in temperature resulting from the energization of the heaterelement closes a normally open heat responsive contact in the generalalarm circuit. k

Still another feature of the invention is the possibility ofdeenergizing, with the rst signal in the above circuit, the signal relaysolenoid so that two of the normally closed contacts complete thepreliminary alarm and latching relay circuits respectively, the generalalarm circuit being not energized as it is interrupted by the open heatresponsive contacts of the time delay device. After a time delaydetermined by the characteristics of the time delay relay, the heatresponsive contact closes. A subsequent signal from any one of themanually operated code stations deenergizes the signal relay a secondtime so that the closing of the contacts completes both the preliminaryand general alarm circuits.

These and other objects, aspects and features will appear vfrom thefollowing description of two practical embodiments illustrating thenovel characteristics of the invention. This description refers to adrawing wherein:

Fig. l is the circuit diagram of one embodiment; and

Fig. 2 a modication of part of the circuit according to Fig. l,indicating a second embodiment of the invention.

As shown in Fig. 1, the initiating circuit of a re alarm systemcomprises a double loop of two spatially parallel conductors II and l2.The adjacent ends rI, r2 of these conductors are joined with respectiveterminals of a terminal resistor R the ohmic characteristics of whichare adjustable. The opposite end of the conductor II is linked directlywith one pole of a power source such as the battery B. The opposite endof the conductor I2 is connected to one terminal of the solenoid I3 of aiirst switching element such as the relay SI. The initiating circuit iscompleted to the opposite pole of the battery B through the solenoid I3,a normally closed contact I4, a sole- .4 noid I8 of a second switchingelement such as the signal relay S2, and the wires I1 and I8.

Energization of the solenoid I3 closes a normally open contact I9thereby to connect a solenoid 2i to the battery B in a circuit includingsolenoid 2| of a transfer station, the Contact I9, the conductor Il, thebattery B and the wires I8 and 22. The energization of the transferstation solenoid 2| unlatches a spring biased detent 23 so that a springactuated code wheel 24 rotates to open the contact I4 and interrupts theinitiating circuit in a manner analogous to that in which a conventionalmanually operated alarm station transmits a coded signal.

The initiating circuit can also be interrupted by any one of a pluralityof manually operated alarm stations A. Each of these stations A includesa spring actuated code wheel 26 with a cammed surface for opening thecontacts 21a and 2lb in a predetermined code sequence and is similar toa conventional alarm station with the exception that the two contactsare used to Open both conductors II and I2 of the initiating circuitrather than a single series contact being used to interrupt the circuitas is the usual practice.

Any number of automatically operated detecting stations D can also beconnected in the same initiating circuit. Several such automaticstations are shown schematically in the drawing each as having anormally open contact 28 which can be closed by a heat responsiveelement 29 thereby to complete a shunting connection between theconductors II and I2. Any or all of these detecting stations D can bereplaced `by devices with normally open contacts operated directly orindirectly when a fire occurs (for example by the ow of water in asprinkler system), or by a con-A tinuous line type detecting cablewherein the conductors contact each other in response to a rise intemperature as is shown in my Patent 2,185,944,

Aor by any of the other well-known types 0f re of contacts @Ga and 30orespectively.

rihe conjoint closing of the contact 38e energizes a locking relay S3 bymeans of a circuit including the relay coil 3i, the normally closedcontact 30o, the wires 32 and I8, the battery B and the wires II and 33.This energization of the coil 3| 4closes the contact 34a to connect aheater element h of a thermal timer T or time delay device of anothertype to the battery B by means of the wires 35, I8, II and 38. A secondcontact 34D closes conjointly with 34a` to provide a holding circuit inparallel with the contact 30e by means of the wires 31 and 38 and thenormally closed manually operated push button switch S6, so that thepower supplied to the heater element h is not interrupted by thesubsequent opening of the contact 30e. As will be recognized by personsskilled in the art it is possible to replace the holding contact and itsassociated circuit with a mechanical latching arrangement to hold thecontact 34a in closed position until manually released.

The preliminary alarm circuit referred to above comprises one or morewarning devices such as the 'bells GI or other audible or visual signalswhich are energized 'from an auxiliary power source such as the batteryBI through nected in series with said power source, one or more manuallyoperated alarm stations, each having two contacts for transmitting asignal by simultaneously opening both of said wires thereby to interruptsaid initiating circuit, one or more automatically operated detectingstations interposed with said alarm stations in said initiating circuit,each adapted to transmit a signal by interconnectingl said wires therebyto change the resistance of said initiating circuit, said initiatingcircuit being arranged as a double loop with at least one contact ofeach alarm station disposed between said power source and theinterconnection between said wires made by any one of said detectingstations, and a switching element energized from said initiating circuitand having a plurality oi contacts operated by a signal from any one ofsaid stations, two of said switching element contacts operating inresponse to a iirst signal to energize the time delay device and thepreliminary alarm circuit respectively from said power source, and athird switching element contact operating in response to signals frommanual stations subsequent to the elapse of the timing period of saidtiming device to complete a circuit including the timing device forenergizing the warning device from said power source, said preliminaryalarm circuit being energized by the simultaneous operating of itscorrelated contact.

3. A fire alarm system of the type continuously energized by a powersource, comprising an alarm vcircuit having a warning device, aninitiating circuit including two wires and a resistor connected inseries with said power source, one or more alarm stations, each havingtwo contacts for transmitting a signal by simultaneously opening both ofsaid wires thereby to interrupt said initiating circuit, one or moredetecting stations interposed with said alarm stations in saidinitiating circuit, each adapted to transmit a signal by interconnectingsaid wires thereby to change the resistance of said initiating circuit,said initiating circuit being arranged as a double loop with at leastone contact of each alarm station disposed between said power source andthe interconnection between said wires made by any one of said detectingstations, and a switching element connected in said initiating circuitand having contacts operated to connect said warning device to saidpower source in response either to the interruption of the initiatingcircuit by a signal from said alarm station or to the change inresistance of the initiating circuit by said detecting station.

4. A lire alarm system of the type continuously energized by a powersource comprising an alarm circuit having a warning device, aninitiating circuit including two wires and a resistor connected inseries with said power source, one or more alarm stations, each havingtwo contacts for transmitting a signal by simultaneously opening both ofsaid wires thereby to interrupt said ini tiating circuit, one or moredetecting stations interposed with said alarm stations in saidinitiating circuit, each adapted to transmit a signal by interconnectingsaid wires thereby to change the resistance of said initiating circuit,said initiating circuit being arranged as a double loop with at leastone contact of each alarm station disposed between said power source andthe interconnection between said wires made by any one of said detectingstations, a rst switching element responsive to signals from any of saiddetecting stations to open said initiating circuit,

and a second switching element connected in said initiating circuit andhaving contacts operated to connect said warning device to said powersource in response to a signal from either the first switching elementor any one of the alarm stations.

5. A iire alarm system of the type continuously energized by a powersource comprising an alarm circuit having a warning device and contactsfor connecting said warning device to said power source, an initiatingcircuit including two wires, a resistor, and a relay solenoid foractuating said contacts connected in series with said power source, oneor more manually operated alarm stations, each having two contacts fortransmitting a signal to said solenoid by simultaneously opening both ofsaid wires thereby to interrupt said initiating circuit, and one or moreautomatically operated detecting stations interposed with said alarmstations in said initiating circuit, each adapted to transmit a signalto said solenoid by interconnecting said wires thereby to change theresistance of said initiating circuit, said initiating circuit beingarranged as a double loop with at least one contact of each alarmstation disposed between said power source and the interconnectionbetween said wires made by any one of said detecting stations, saidsolenoid operated contacts being actuated in response to signals fromany one of said stations thereby to energize the warning device fromsaid power Source.

6. A re alarm system of the type continuously energized by a powersource comprising an alarm circuit having a warning device and a. rstrelay contact for connecting said device to said power source, aninitiating circuit including two wires, a resistor and a marginal relaysolenoid for closing said contact when deenergized connected in serieswith said power source, one or more manually operated alarm stations,each having two contacts lor transmitting a coded signal to saidsolenoid by simultaneously opening both of said wires thereby tointerrupt said initiating circuit, one or more automatically operateddetecting stations interposed with said alarm stations in saidinitiating circuit, each adapted to transmit a continuous signal byinterconnecting said wires thereby to change the resistance of saidinitiating circuit, said initiating circuit being arranged as a doubleloop with at least one contact o each alarm station disposed betweensaid power source and the interconnection between said wires made by anyone of said detecting stations, an automatically operated transferstation for interrupting said initiating circuit to transmit a codedsignal to said solenoid, and a second relay contact closed by theenergization of the solenoid by a continuous signal from any one of thedetecting stations to operate the transfer station, said iirst relaycontact being actuated to energize the alarm circuit from said powersource upon deenergization of the solenoid by interruption of theinitiating circuit by a coded signal from either the transfer station orfrom any one of the manually operated stations.

7. A fire alarm system oi the type continuously energized by a powersource comprising an alarm circuit having a warning device and a contactfor connecting said device to said power source, an initiating circuitincluding two wires, a resistor, a relay solenoid for closing saidcontact when deenergized and a second relay solenoid connected in serieswith said power source; one or more manually operated alarm stations,each having two contacts for transmitting a coded signal bysimultaneously opening both of said wires thereby to interrupt saidinitiating circuit; one or more automatically operated detectingstations interposed with said alarm stations in said initiating circuit,each adapted to transmit a continuous signal by interconnecting saidwires thereby to decrease the resistance of said initiating circuit;said initiating circuit being arranged as a double loop with at leastone contact of each alarm station disposed between said power source andthe interconnection between said wires made by any one of said detectingstations; an automatically operated trip station for interrupting saidinitiating circuit to transmit a coded signal to the iirst solenoid; anda second relay contact closed upon the energization of the secondsolenoid by a continuous signal from any one of the detecting stationsto operate the trip station, said :first relay contact being actuated toenergize the alarm circuit from said power source upon deenergization ofthe first relay solenoid by the interruption of the initiating circuitby a coded signal from either the trip station or from any one of themanually operated alarm stations.

8. A lire alarm system of the type having a plurality of alarm stationsfor interrupting a continuously energized initiating circuit to transmita signal, comprising a preliminary alarm circuit, a power source forenergizing said circuit, a general alarm circuit including a warningdevice and a time delay device operating a predetermined period afterbeing energized from said source, and a switching element energized fromsaid initiating circuit and having a plurality or contacts operated by asignal from any one of said stations, two of said contacts operating inresponse to a rst signal to energize both the time delay device and thepreliminary alarm circuit from said power source, the third contactoperating in response to signals from manual stations subsequent to theelapse of the timing period of said timing device to complete a circuitincluding the timing device. for energizing the warning device from saidpower source, said preliminary alarm circuit being energized by thesimultaneous operating of its correlated contact.

9. a nre alarm system of the type having a plurality or alarm stationsfor interrupting a continuously energized initiating circuit totransinit a signal, comprising a power source; a signal relay having asolenoid connected in the initiating circuit and three contacts openedby the energiaation of said solenoid; a preliminary alarm circuit; ageneral alarm circuit, each of said alarm circuits including a warningdevice energized from the power source by the closing of a respectiveone or said signal relay contacts, a time delay device includingcontacts connected to the warning device in the general alarm circuitand a timing element for operating said device contacts a predeterminedperiod after being energized from the power source by said third signalrelay contact so that the rst signal from any one of said stationsenergizes the preliminary alarm circuit warning device and the timingelement to start said time interval and signals from any one of saidalarm stations transmitted subsequent to the elapse of the periodenergizing the warning devices in both the preliminary and general alarmcircuits.

WILLIS GERALD HOLMES.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 4184,14() Cortland Oct. 11, 18921,239,381 Francis Sept. 4, 1917 1,536,191 Derby May 5, 1925 1,536,192Derby May 5, 1925 1,977,121 Ekman Oct. 16, 1934

